I guess some definitions of "quite simple" can be applied to that code. It looks more like "clever" to me. (:
I rejected using 'grep' at all since it seems likely to me that there could be cases where there is nothing to trim from the front. Your solution (and any simple 'grep' solution) will produce nothing for that case (or else can't deal with extra, unexpected leading garbage). I also dislike solutions that I can tell will require fundamental changes in the face of simple changes to the requirements.